New hydroxybenanomicins produced by Actinomadura

A soil microorganism, Actinomadura sp. MH193-16F4, produces an antifungal antibiotic benanomicin A and several related compounds. Among them, benanomicin A is the best candidate as a chemotherapeutic agent in terms of antifungal activity, toxicity and water-solubility. Three novel hydroxyl congeners, 3'-hydroxybenanomicin A, 7-hydroxybenanomicin A and 7-hydroxybenanomicinone have been isolated from the culture broth of the MH193-16F4 strain or its mutant. Interestingly, 3'-hydroxy-benanomicin A was as effective as benanomicin A, but the 7-hydroxy congeners were inactive. The inactive congeners differ from benanomicin A and 3'-hydroxyenanomicin A in their conformational structures at C-5 and C-6.